Morgan-Richards Mary, Trewick Steve A, Bartosch-Härlid Anna, Kardailsky Olga, Phillips Matthew J, McLenachan Patricia A, Penny David
Allan Wilson Center for Molecular Ecology and Evolution, Massey University, Palmerston North, New Zealand.
BMC Evol Biol. 2008 Jan 23;8:20. doi: 10.1186/1471-2148-8-20.
Evolutionary biologists are often misled by convergence of morphology and this has been common in the study of bird evolution. However, the use of molecular data sets have their own problems and phylogenies based on short DNA sequences have the potential to mislead us too. The relationships among clades and timing of the evolution of modern birds (Neoaves) has not yet been well resolved. Evidence of convergence of morphology remain controversial. With six new bird mitochondrial genomes (hummingbird, swift, kagu, rail, flamingo and grebe) we test the proposed Metaves/Coronaves division within Neoaves and the parallel radiations in this primary avian clade.
Our mitochondrial trees did not return the Metaves clade that had been proposed based on one nuclear intron sequence. We suggest that the high number of indels within the seventh intron of the beta-fibrinogen gene at this phylogenetic level, which left a dataset with not a single site across the alignment shared by all taxa, resulted in artifacts during analysis. With respect to the overall avian tree, we find the flamingo and grebe are sister taxa and basal to the shorebirds (Charadriiformes). Using a novel site-stripping technique for noise-reduction we found this relationship to be stable. The hummingbird/swift clade is outside the large and very diverse group of raptors, shore and sea birds. Unexpectedly the kagu is not closely related to the rail in our analysis, but because neither the kagu nor the rail have close affinity to any taxa within this dataset of 41 birds, their placement is not yet resolved.
Our phylogenetic hypothesis based on 41 avian mitochondrial genomes (13,229 bp) rejects monophyly of seven Metaves species and we therefore conclude that the members of Metaves do not share a common evolutionary history within the Neoaves.
进化生物学家常常被形态学上的趋同现象误导，这在鸟类进化研究中很常见。然而，分子数据集的使用也有其自身问题，基于短DNA序列构建的系统发育树也有可能误导我们。现代鸟类（新鸟亚纲）各分支之间的关系以及进化时间尚未得到很好的解决。形态学趋同的证据仍存在争议。我们利用六个新的鸟类线粒体基因组（蜂鸟、雨燕、鹭鹤、秧鸡、火烈鸟和䴙䴘）来检验新鸟亚纲中提出的Metaves/Coronaves分类以及这个主要鸟类分支中的平行辐射。
我们的线粒体树没有得出基于一个核内含子序列所提出的Metaves分支。我们认为，在这个系统发育水平上，β-纤维蛋白原基因第七内含子内的插入缺失数量过多，导致数据集中所有分类群没有一个共同的比对位点，从而在分析过程中产生了假象。关于整个鸟类系统发育树，我们发现火烈鸟和䴙䴘是姐妹分类群，且位于鸻形目（滨鸟）的基部。使用一种新颖的位点去除技术进行降噪处理后，我们发现这种关系是稳定的。蜂鸟/雨燕分支位于大型且非常多样化的猛禽、岸鸟和海鸟群体之外。出乎意料的是，在我们的分析中，鹭鹤与秧鸡的关系并不密切，但由于鹭鹤和秧鸡在这个包含了41种鸟类的数据集中都与任何分类群没有密切关联，它们在系统发育树上的位置尚未确定。
我们基于41个鸟类线粒体基因组（13229个碱基对）的系统发育假说否定了七种Metaves物种的单系性，因此我们得出结论，Metaves的成员在新鸟亚纲中没有共同的进化历史。
